For this question, I'm using the magic system discussed here that I will sum up with this: you take energy from your environment (e.g. heat from the atmosphere) and transform it into another form to cast a variety of spells. The spell itself must be either pure energy or resulting from said energy.
One particular spell is hard light, which is the purpose of this question. However, I'm having a hard time determining how I could generate hard light in compliance with the rules of my universe.
So here is what hard light is and isn't:
- It is solid. Not necessarily in the physical sense of the word, but hard light collides with any physical object, include other hard light objects.
- It glows. It generates faint light (as opposed to reflecting it).
- It is cold. It isn't a freezing hazard though.
- It does block what a wall would block. Besides, physical objects, this includes energy, e.g. heat.
- It doesn't block what a wall wouldn't block. E.g. radio signals.
- It only causes blunt force trauma, much unlike a light saber.
- It is a constant-cast spell. If the caster stops casting, hard light dissipates. Ideally, does not persist, though it could take a few seconds to dissipate.
- It is moderately translucent, as in opaque glass translucent.
- It is not a block of ice. That would be just too easy.
- It is not solid light, unless solid light actually exists and would meet other requirements.
I've noted in italic requirements you can play with if you have to.
The rules of magic here are:
- Assume magic always works as advertised.
- Assume the caster is not hurt by their spells.
- Assume there is always just the right amount of energy to do what you want to do.
- You can only transform energy. As such, a spell is energy, a discharge of energy or anything energy-related.
- Outside of the aforementioned magic, assume rules of physics apply.
Given all that, what could be the physical nature of hard light?